This application claims priority from Japanese Patent Applications No. hei 6-289,093 filed in Japan on Oct. 28, 1994, and No. hei 8-69070 filed in Japan on Feb. 28, 1996, the complete disclosures of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a layered molding formed of a fluoroplastic layer or a polyamide plastic layer and a rubber layer and that exhibits excellent anti-permeability to gasoline and alcohol-containing gasoline.
2. Description of Related Art
Fuel hoses are commonly used in a fuel circuit of an automobile (including low/high pressure applications), as well as at service stations as an inlet hose or as an inlet port for introducing gasoline into the gasoline tank of automobiles. In order to prevent fuel from permeating through the fuel hose and spilling onto the user or an automobile, the fuel hose must be prepared from a material that resist gasoline penetration or permeability thereof. In order to accomplish these objectives, fluoroplastic having a tertiary composition and fluoro-rubber are well-known for their excellent anti-permeability to gasoline. However, these materials are very expensive.
It has been discovered that fluoroplastic material maintains a constant anti-permeability level to gasoline irrespective of the thickness of the material, so long as the thickness remains not less than a predetermined minimum operational thickness. By contrast, the anti-permeability of fluoro-rubber is much more dependent upon the thickness of the hose. Accordingly, hoses formed from fluoro-rubber must have a relatively large thickness, resulting in higher production cost.
In order to provide a fuel hose having excellent anti-permeability to gasoline and low production costs, it has been proposed to prepare the layered molding from two layers formed from different materials--e.g., an inner fluoroplastic layer having a small thickness and an outer, inexpensive rubber layer (e.g., epichlorohydrin rubber) having excellent fire, weather and cold proofing properties.
However, several problems are associated with the aforementioned two layered molding. For example, fluoroplastic does not adequately adhere to inexpensive rubber such as an epichlorohydrin rubber. Accordingly, as shown in FIG. 4, when forming a conventional fuel hose 9, it is necessary to use an adhesive agent 4 for securing a fluoroplastic inner layer 2 and an epichlorohydrin rubber outer layer 3. The fluoroplastic also requires surface treatment for improving its adhesive strength with respect to the rubber outer layer 3.